Average column density of H${}_2^{18}$O at 80–120 au under different condensation rates (f_cond). The vertical gray band indicates the time range when observing the intensity shoulder. The dashed black line denotes the average column density derived from ALMA band 5 data by Tobin et al. (2023) with 1σ uncertainty shaded in gray. Dotted gray line denotes the best-fit value in static snowline model.